3.1 Hypertension & Cardiovascular Disorders

3.1 Hypertension & Cardiovascular Disorders

Core Clinical Rule: In Black African populations without chronic kidney disease or heart failure, initial monotherapy for essential hypertension should be a dihydropyridine Calcium Channel Blocker (CCB) or a thiazide-like diuretic. Conversely, whenever diabetes mellitus with microalbuminuria or chronic kidney disease is identified, an ACE inhibitor or ARB is mandatory first-line to preserve renal architecture. In hypertensive emergencies, never reduce blood pressure precipitously; target a 20% to 25% reduction in Mean Arterial Pressure (MAP) over the first hour.

Cardiovascular diseases (CVDs) represent the fastest-growing non-communicable disease (NCD) threat in Kenya. According to the Kenya National STEPwise Survey for NCD Risk Factors, the national prevalence of hypertension among adults aged 18 to 69 years is approximately 24.5%, with over 56% of affected individuals unaware of their diagnosis. For the Clinical Officer intern, mastering protocolized cardiovascular diagnosis, pharmacotherapy, and emergency resuscitation is essential for hospital rounds and licensure examinations.

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1. Kenya National NCD Guidelines for Hypertension

Accurate Blood Pressure Measurement Technique

A valid diagnosis of hypertension requires adherence to standard clinical measurement protocols:

• The patient must rest quietly in a seated position with back supported and feet flat on the floor for at least 5 minutes prior to measurement.
• Avoid caffeine consumption, smoking, and vigorous exercise for at least 30 minutes before testing.
• Use a validated upper-arm device with an appropriately sized cuff (bladder length >= 80% and width >= 40% of mid-upper arm circumference). An undersized cuff causes falsely elevated readings.
• Position the arm supported at heart level (mid-sternum).
• Take two readings separated by 1 to 2 minutes; if they differ by > 5 mmHg, obtain a third and calculate the average.
• Diagnostic confirmation requires elevated readings across >= 2 separate clinical visits separated by 1 to 4 weeks, unless Stage 2 hypertension with target organ damage or a Hypertensive Crisis is present on initial encounter.

Diagnostic Staging and Initial Management

Clinical Evaluation and Target Organ Damage (TOD)

Every newly diagnosed hypertensive patient requires baseline screening to identify secondary etiologies and subclinical end-organ injury:

• Fundoscopy: Keith-Wagener-Barker classification (Grade 1: arteriolar narrowing; Grade 2: arteriovenous nicking; Grade 3: flame hemorrhages, cotton-wool spots, hard exudates; Grade 4: papilledema).
• Renal Function: Urinalysis for protein, blood, and microalbuminuria (urinary albumin-to-creatinine ratio [uACR] 30–300 mg/g); serum creatinine and estimated glomerular filtration rate (eGFR).
• Metabolic Profile: Fasting blood glucose, glycated hemoglobin (HbA1c), fasting lipid profile (total cholesterol, LDL, HDL, triglycerides), and serum uric acid.
• Cardiovascular Workup: 12-lead resting ECG to detect Left Ventricular Hypertrophy (LVH) using the Sokolow-Lyon criteria ($SV_1 + [RV_5 \text{ or } RV_6] > 35\text{ mm}$) or Cornell voltage criteria ($R_{aVL} + SV_3 > 28\text{ mm}$ in men, $> 20\text{ mm}$ in women).

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2. Pharmacotherapy: Regimens, Mechanisms, and Population Nuances

                              [Confirmed Hypertension >= 140/90 mmHg]
                                                |
               +--------------------------------+--------------------------------+
               |                                                                 |
       [No CKD or Diabetes]                                            [CKD or Diabetes Mellitus
               |                                                        with Microalbuminuria]
       [Black African Origin]                                                    |
               |                                                      [First-Line: ACEi or ARB]
    +----------+----------+                                           (Enalapril 5-20 mg daily or
    |                     |                                            Losartan 50-100 mg daily)
[First-Line CCB]   [Thiazide Diuretic]                                           |
(Amlodipine 5-10 mg) (HCTZ 12.5-25 mg / Indapamide 1.5-2.5 mg)                   v
    |                     |                                           [If BP Uncontrolled]
    +----------+----------+                                           Add CCB or Thiazide-like
               v                                                              Diuretic
    [If BP Uncontrolled: Dual Therapy]
       CCB + ACEi/ARB or CCB + Thiazide

First-Line Antihypertensive Classes

1. Dihydropyridine Calcium Channel Blockers (CCBs):

   • Agents & Dosages: Amlodipine 5–10 mg PO once daily; Nifedipine retard 20–40 mg PO twice daily.
   • Mechanism: Selectively inhibits L-type voltage-gated calcium channels in vascular smooth muscle, causing potent peripheral arterial vasodilation.
   • Clinical Placement: First-line drug of choice in Black African patients without heart failure or CKD. Low-renin hypertension in this demographic responds significantly better to CCBs than to ACE inhibitors.
   • Adverse Effects: Dependent peripheral pedal edema (caused by precapillary arteriolar dilation, not fluid retention; unresponsive to loop diuretics), headache, facial flushing, gingival hyperplasia.

2. Angiotensin Converting Enzyme Inhibitors (ACEis) & Angiotensin Receptor Blockers (ARBs):

   • Agents & Dosages: Enalapril 5–20 mg PO daily (single or divided BID); Lisinopril 10–40 mg PO daily; Losartan 50–100 mg PO daily; Telmisartan 40–80 mg PO daily.
   • Mechanism: ACEis prevent conversion of angiotensin I to angiotensin II and inhibit bradykinin degradation. ARBs selectively block the angiotensin II type-1 ($AT_1$) receptor.
   • Clinical Placement: Compelling indication in Diabetes Mellitus with microalbuminuria (uACR > 30 mg/g), Chronic Kidney Disease (stages 1–3), Heart Failure (HFrEF), and post-Myocardial Infarction. They preferentially dilate the efferent arteriole, reducing intraglomerular capillary hydrostatic pressure and halting diabetic glomerulosclerosis.
   • Adverse Effects & Monitoring: Dry hacking cough (10–20% of patients on ACEi due to bradykinin/substance P accumulation; switch to ARB), hyperkalemia, and angioedema (subcutaneous swelling of lips, tongue, and larynx; higher incidence in Black African individuals). Serum creatinine and potassium must be re-checked 1 to 2 weeks after initiation; an elevation in serum creatinine up to 30% above baseline is acceptable hemodynamic adaptation.
   • Contraindications: Strictly contraindicated in pregnancy (fetal renal dysgenesis, oligohydramnios, skull hypoplasia, intrauterine growth restriction) and bilateral renal artery stenosis (causes acute renal shutdown by abolishing angiotensin II-mediated efferent arteriolar constriction).

3. Thiazide and Thiazide-Like Diuretics:

   • Agents & Dosages: Hydrochlorothiazide (HCTZ) 12.5–25 mg PO once daily; Indapamide 1.5–2.5 mg PO once daily; Chlorthalidone 12.5–25 mg PO once daily.
   • Mechanism: Inhibits the $Na^+/Cl^-$ cotransporter in the early distal convoluted tubule, promoting natriuresis and long-term reduction in peripheral vascular resistance.
   • Adverse Effects: Hypokalemia, hyponatremia, hypomagnesemia, hyperuricemia (can precipitate acute gouty arthritis), hyperglycemia, and hyperlipidemia.

4. Hypertension in Pregnancy:

   • First-line safe oral agents: Methyldopa (250–500 mg PO 8-hourly; max 2 g/day), Labetalol (100–400 mg PO 12-hourly), and Nifedipine retard (10–20 mg PO 12-hourly). ACE inhibitors, ARBs, direct renin inhibitors, and spironolactone are absolutely contraindicated.

Hypertensive Crisis: Urgency versus Emergency

• Hypertensive Urgency (BP >= 180/120 mmHg without acute target organ damage):
  • Management: Patient is placed in a quiet room for 30 minutes. Re-evaluate. Titrate oral antihypertensive agents (e.g., Amlodipine 5–10 mg PO, Captopril 25 mg PO, or Labetalol 100–200 mg PO). Aim to reduce blood pressure gradually over 24 to 48 hours.
  • Safety Warning: Sublingual Nifedipine is strictly contraindicated due to rapid, unpredictable precipitous drops in perfusion pressure leading to watershed ischemic stroke, myocardial infarction, and death.
• Hypertensive Emergency (BP >= 180/120 mmHg with acute target organ damage):
  • Target Organ Damage Presentations: Acute aortic dissection, acute cardiogenic pulmonary edema, acute coronary syndrome, hypertensive encephalopathy, acute intracerebral hemorrhage, acute ischemic stroke, or acute renal failure.
  • Hemodynamic Target: Calculate Mean Arterial Pressure ($MAP = DBP + \frac{1}{3}[SBP - DBP]$). Reduce MAP by no more than 20% to 25% within the first hour. If stable, reduce toward 160/100 mmHg over the next 2 to 6 hours, and normalize over 24 to 48 hours.
  • Exceptions to Gradual Reduction: In acute aortic dissection, rapidly reduce SBP to < 120 mmHg and heart rate to < 60 bpm within 20 minutes (using IV beta-blockade first e.g., labetalol or esmolol). In acute ischemic stroke, permit permissive hypertension (do not treat unless BP > 220/120 mmHg, or > 185/110 mmHg if intravenous thrombolysis is planned).
  • Parenteral Antihypertensive Agents:
    • IV Labetalol: 20 mg slow IV bolus over 2 minutes, followed by 40–80 mg IV every 10 minutes (max cumulative dose 300 mg), or continuous infusion at 0.5–2 mg/min.
    • IV Hydralazine: 5–10 mg slow IV bolus every 20–30 minutes (especially useful in severe pre-eclampsia/eclampsia; watch for reflex tachycardia).
    • IV Nitroglycerin: 5–100 mcg/min continuous infusion; agent of choice for acute pulmonary edema or acute coronary syndrome.

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3. Heart Failure with Reduced Ejection Fraction (HFrEF)

Heart Failure with Reduced Ejection Fraction is defined by clinical signs and symptoms of heart failure alongside an echocardiographic Left Ventricular Ejection Fraction (LVEF) <= 40%.

Clinical Presentation and Framingham Diagnostic Criteria

Diagnosis requires the presence of at least 2 Major criteria OR 1 Major + 2 Minor criteria:

• Major Criteria: Paroxysmal Nocturnal Dyspnea (PND), orthopnea, elevated Jugular Venous Pressure (JVP > 4 cm above sternal angle), hepatojugular reflux, third heart sound ($S_3$ gallop), cardiomegaly (displaced apex beat lateral to midclavicular line), bibasilar pulmonary crackles, acute pulmonary edema, weight loss >= 4.5 kg in 5 days in response to diuretics.
• Minor Criteria: Bilateral ankle edema, nocturnal cough, dyspnea on ordinary exertion, hepatomegaly, pleural effusion, tachycardia (HR > 120 bpm), decrease in vital capacity by one-third.

Guideline-Directed Medical Therapy (GDMT): The Four Pillars

Every patient with stable HFrEF must be initiated and up-titrated on the four foundational drug classes proven to reduce all-cause and cardiovascular mortality:

+-----------------------------------------------------------------------------------+
|            THE FOUR MORTALITY-REDUCING PILLARS OF GDMT IN HFrEF                   |
+-----------------------------------------------------------------------------------+
| 1. ARNI / ACEi / ARB        | Sacubitril/Valsartan 24/26 mg to 97/103 mg PO BID   |
|                             | (Requires 36-hr ACEi washout) OR Enalapril 2.5-20mg |
+-----------------------------+-----------------------------------------------------+
| 2. Evidence-Based Beta-Blocker | Carvedilol 3.125-25mg BID, Metoprolol Succinate   |
|                             | 12.5-200mg daily, or Bisoprolol 1.25-10mg daily     |
+-----------------------------+-----------------------------------------------------+
| 3. MRA                      | Spironolactone 12.5-50 mg PO daily                  |
|                             | (Monitor K+; hold if K+ > 5.0 mmol/L or eGFR < 30)  |
+-----------------------------+-----------------------------------------------------+
| 4. SGLT2 Inhibitor          | Dapagliflozin 10 mg PO daily or Empagliflozin 10 mg |
|                             | (Benefits independent of diabetic status)           |
+-----------------------------------------------------------------------------------+
| SYMPTOMATIC DECONGESTION: Loop Diuretic (Furosemide 20-80 mg daily) relieves volume|
| overload and dyspnea, but does NOT reduce long-term mortality on its own.         |
+-----------------------------------------------------------------------------------+

Beta-Blocker Initiation Precaution: Never initiate or up-titrate beta-blockers during an acute decompensated "wet and cold" exacerbation. Wait until the patient is euvolemic, compensated, and stabilized on diuretics.

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4. Acute Coronary Syndromes (ACS)

Acute Coronary Syndrome encompasses a clinical spectrum of myocardial ischemia triggered by atherosclerotic plaque rupture, ulceration, and overlying thrombus formation.

ACS Spectrum and Diagnostic Differentiation

1. STEMI (ST-Elevation Myocardial Infarction): Transmural myocardial ischemia resulting in persistent ST-segment elevation (>= 1 mm in >= 2 contiguous limb leads, or >= 2 mm in precordial leads $V_2-V_3$) or new-onset Left Bundle Branch Block (LBBB), accompanied by elevated cardiac biomarkers (cardiac troponin I or T).
2. NSTEMI (Non-ST-Elevation Myocardial Infarction): Subendocardial ischemia presenting with ST-segment depression, T-wave inversion, or non-specific ST changes, alongside elevated cardiac troponin.
3. Unstable Angina: Angina at rest (> 20 minutes), new-onset severe angina, or crescendo angina, without elevation in cardiac biomarkers.

ECG Lead Localization and Coronary Anatomy

Emergency Management Protocol (MONA + Dual Antiplatelet Therapy)

• M (Morphine): 2–4 mg IV slow push for severe refractory chest pain. Use cautiously; delays oral antiplatelet absorption and suppresses respiratory drive.
• O (Oxygen): Administer only if $SpO_2 < 90%$ or in overt respiratory distress. Hyperoxia induces coronary vasoconstriction and increases reperfusion injury.
• N (Nitrates): Sublingual Nitroglycerin 0.4 mg (or 500 mcg) every 5 minutes up to 3 doses. Transition to IV infusion (5–100 mcg/min) for refractory pain or pulmonary edema. Strict Contraindications: Systolic BP < 90 mmHg, bradycardia (HR < 50 bpm), tachycardia (HR > 100 bpm), suspected Right Ventricular Infarction, or phosphodiesterase-5 inhibitor use (sildenafil within 24 hours, tadalafil within 48 hours).
• A (Aspirin): 300 mg chewable non-enteric coated loading dose immediately, followed by 75–100 mg daily indefinitely.
• Dual Antiplatelet Therapy (DAPT): Add a $P2Y_{12}$ inhibitor: Clopidogrel 300 mg loading dose (600 mg if proceeding to primary PCI; 75 mg if age > 75 receiving thrombolysis), followed by 75 mg PO daily for 12 months.
• Anticoagulation: Subcutaneous Enoxaparin 1 mg/kg every 12 hours (with initial 30 mg IV bolus in STEMI age < 75), or Unfractionated Heparin (60 U/kg IV bolus, max 4000 U, then 12 U/kg/h infusion titrated to aPTT 1.5–2.0x control).
• Reperfusion Strategies:
  • Primary PCI: Reperfusion method of choice if First Medical Contact (FMC)-to-device time is < 120 minutes (door-to-balloon < 90 minutes).
  • Fibrinolysis / Thrombolysis: Indicated for STEMI presenting within 12 hours of symptom onset if primary PCI cannot be performed within 120 minutes. Door-to-needle target is < 30 minutes. Regimen: Streptokinase 1.5 million IU in 100 mL $5%$ dextrose infused IV over 60 minutes, or weight-adjusted Tenecteplase. Absolute Contraindications: Prior intracranial hemorrhage, ischemic stroke within 6 months, CNS neoplasm or arteriovenous malformation, major trauma/surgery/head injury within 3 weeks, active internal bleeding (excluding menses), or suspected aortic dissection.

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5. Acute Rheumatic Fever (ARF) & Rheumatic Heart Disease (RHD)

Acute Rheumatic Fever is an autoimmune, multi-system inflammatory sequela occurring 2 to 4 weeks after an untreated pharyngeal infection with Group A Beta-Hemolytic Streptococcus (GABHS / Streptococcus pyogenes). Molecular mimicry between streptococcal M-protein epitopes and human cardiac myosin, valvular endothelium, and laminin triggers immune-mediated tissue injury.

2015 Modified Jones Criteria for High/Moderate-Risk Populations (e.g., Kenya)

Confirmation requires documentation of preceding GABHS pharyngitis (elevated/rising Antistreptolysin O [ASO] titer > 200–400 IU/mL, positive throat culture, or positive rapid antigen test) PLUS:

• Two Major criteria, OR
• One Major + Two Minor criteria.

+-----------------------------------------------------------------------------------+
|                    2015 MODIFIED JONES CRITERIA (KENYA / HIGH RISK)               |
+-----------------------------------------------------------------------------------+
| MAJOR CRITERIA:                                                                   |
| 1. Carditis (Clinical e.g. murmur of MR/AR, pericarditis, HF; or subclinical echo) |
| 2. Polyarthritis OR Monoarthritis / Polyarthralgia (High-risk population rule)    |
| 3. Sydenham Chorea (Rapid, purposeless, involuntary movements; emotional lability) |
| 4. Erythema Marginatum (Non-pruritic serpiginous macules with pale centers)       |
| 5. Subcutaneous Nodules (Painless, firm nodules over bony extensor surfaces)      |
+-----------------------------------------------------------------------------------+
| MINOR CRITERIA:                                                                   |
| 1. Fever (>= 38.0°C)                                                              |
| 2. Arthralgia (Only if arthritis is not used as a major criterion)                |
| 3. Elevated Acute Phase Reactants: ESR >= 30 mm/hr and/or CRP >= 3.0 mg/dL        |
| 4. Prolonged PR Interval on ECG (Unless carditis is used as a major criterion)    |
+-----------------------------------------------------------------------------------+
| *Chorea or indolent carditis presenting late can establish the diagnosis alone.   |
+-----------------------------------------------------------------------------------+

Acute Management & Secondary Prophylaxis

• Acute Therapy: Strict bed rest. High-dose Aspirin (80–100 mg/kg/day in children divided 6-hourly; 4–6 g/day in adults) for arthritis, tapered over 4 to 6 weeks. Systemic corticosteroids (Prednisolone 1–2 mg/kg/day PO) are indicated for severe carditis with cardiomegaly or heart failure. Eradicate pharyngeal GAS carriage with a single dose of intramuscular Benzathine Penicillin G.
• Chronic Rheumatic Heart Disease: Chronic recurrent valvulitis results in permanent valvular destruction. The mitral valve is involved in > 90% of cases (isolated mitral regurgitation in children/adolescents; mitral stenosis with classic 'fish-mouth' orifice and hockey-stick anterior leaflet in chronic adult disease), followed by the aortic valve.
• Secondary Antibiotic Prophylaxis (Mandatory Kenya MOH / WHO Protocol):
  • Drug of Choice: Benzathine Penicillin G 1.2 million IU IM (600,000 IU for children < 27–30 kg) every 3 to 4 weeks (every 3 weeks is preferred in high-prevalence settings like Kenya due to waning serum levels by week 4).
  • Penicillin Allergy: Oral Erythromycin 250 mg PO twice daily or Azithromycin 250 mg daily.
  • Prophylaxis Duration:
    • ARF without Carditis: Minimum of 5 years after last attack or until age 21 (whichever is longer).
    • ARF with Carditis (no permanent valve disease): Minimum of 10 years after last attack or until age 21 (whichever is longer).
    • RHD with Persistent Valvular Disease: Minimum of 10 years after last attack or until age 40, or lifelong if severe disease or high environmental exposure risk.